Technology Reference Guide

What is it?
Tape subsystems generally consist of a magnetic tape transport, interface, and associated software. Most of the systems in common use on PC networks are cartridge tape units using 4mm or 8mm tape. Tape subsystems may use their own controller, or may be attached to the SCSI disk controller in the server. The speed at which a tape can back up data can be a concern, since there is generally a limited amount of time to backup a system when it is not being accessed by users. The choice of backup software is generally determined by the flexibility of the software in offering backup and restore options, as well as compatibility with the network operating system. The network operating system may offer a backup utility for use with the tape unit. Utilities may also be bundled with the tape unit, or purchased separately from a third party.

What does it do?
The primary use of the tape subsystem is to record and store backup copies of the data resident on hard disks. In case of a disk failure, the replacement disk can be re-loaded from tape, and all the files restored. The success of this process relies on the discipline associated with backing up the system. In a heavy transaction-oriented environment, even a consistent routine for nightly backups can still cause a significant data loss if a disk fails in the late afternoon.

The secondary purpose of tape storage is to archive files. When a company changes accounting periods, or simply runs out of disk space, it may choose to archive files that are no longer being accessed, but must still be retained. This frees up needed disk space, and provides a low-cost method of storing data.

How is it used?
A tape subsystem is used to provide low-cost, off-line storage of data. Any system that does not have a tape backup system, and a routine to use it, runs the risk of losing all the data stored on it. Because of the need to insure that backups are routinely done, backup software may provide the ability to automate the process, and run unattended backups according to a pre-defined schedule. Tape units may be attached to a workstation on the network, and used to back up the file server. Tape units may be attached to the server, and be able to back up its own disks, other servers on the network, and even workstations.

Tape units are also useful for providing removable storage for archived files. Because the tape cartridges are easily portable, they can be stored in a secure location separate from the systems, and in the event of a catastrophic event, can be used to restore the computing environment.

Where do I get more information?
Contact your local CBV Office.

	Technology Reference Guide 2. Hardware F. Tape Subsystems